BACKGROUND: Plastid terpenoids in plants are synthesised via the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway. To date, no study has investigated the role of microRNA (miRNA) regulation in this pathway under different light conditions, particularly in the context of MEP-derived terpenoid content and photosynthesis. This study investigates how miRNAs regulate two key MEP pathway genes: 1-DEOXY-D-XYLULOSE-5-PHOSPHATE SYNTHASE 1 (DXS1) and GERANYLGERANYL DIPHOSPHATE SYNTHASE 2 (GGPPS2) under high-intensity light and prolonged darkness. METHODS AND RESULTS: In silico analysis revealed that miR826b targets DXS1 and miR2937 targets GGPPS2. To investigate their roles, the short tandem target mimic (STTM) approach was used in Arabidopsis to suppress the expression of miR826b and miR2937, generating single and double STTM transgenic lines. In all light treatments, the expression of miR826b and miR2937 was successfully downregulated in the STTM lines. However, the expression of DXS1 increased under fluctuating light, while the expression of GGPPS2 increased exclusively in double STTM plants. Chlorophyll content decreased under both high light intensity and darkness, while carotenoids increased only under high light intensity. Remarkably, the STTM826b + 2937 lines exhibited increased chlorophyll and carotenoid levels under both conditions and showed enhanced photosynthetic adaptation compared to the wild-type (WT) and single STTM lines. CONCLUSIONS: These results indicate that suppression of miR826b and miR2937 by STTM modulates the MEP pathway in plastid terpenoid regulation and its impact on photosynthesis. This study lays the foundation for further exploration of miRNA-mediated control of plastid terpenoid in response to light.
Plants have developed diverse physical and chemical defence mechanisms to ensure their continued growth and well-being in challenging environments. Plants also have evolved intricate molecular mechanisms to regulate their responses to biotic stress. Non-coding RNA (ncRNA) plays a crucial role in this process that affects the expression or suppression of target transcripts. While there have been numerous reviews on the role of molecules in plant biotic stress, few of them specifically focus on how plant ncRNAs enhance resistance through various mechanisms against different pathogens. In this context, we explored the role of ncRNA in exhibiting responses to biotic stress endogenously as well as cross-kingdom regulation of transcript expression. Furthermore, we address the interplay between ncRNAs, which can act as suppressors, precursors, or regulators of other ncRNAs. We also delve into the regulation of ncRNAs in response to attacks from different organisms, such as bacteria, viruses, fungi, nematodes, oomycetes, and insects. Interestingly, we observed that diverse microorganisms interact with distinct ncRNAs. This intricacy leads us to conclude that each ncRNA serves a specific function in response to individual biotic stimuli. This deeper understanding of the molecular mechanisms involving ncRNAs in response to biotic stresses enhances our knowledge and provides valuable insights for future research in the field of ncRNA, ultimately leading to improvements in plant traits.
The application of miRNA mimic technology for silencing mature miRNA began in 2007. This technique originated from the discovery of the INDUCED BY PHOSPHATE STARVATION 1 (IPS1) gene, which was found to be a competitive mimic that prevents the cleavage of the targeted mRNA by miRNA inhibition at the post-transcriptional level. To date, various studies have been conducted to understand the molecular mimic mechanism and to improve the efficiency of this technology. As a result, several mimic tools have been developed: target mimicry (TM), short tandem target mimic (STTM), and molecular sponges (SPs). STTM is the most-developed tool due to its stability and effectiveness in decoying miRNA. This review discusses the application of STTM technology on the loss-of-function studies of miRNA and members from diverse plant species. A modified STTM approach for studying the function of miRNA with spatial-temporal expression under the control of specific promoters is further explored. STTM technology will enhance our understanding of the miRNA activity in plant-tissue-specific development and stress responses for applications in improving plant traits via miRNA regulation.